RESEARCH ARTICLE Asymptomatic COVID-19 in the elderly: dementia and viral clearance as risk factors for disease progression. [version 1; peer review: awaiting peer review] Ignacio Esteban 1 , Georgina Bergero 1 , Camila Alves 1 , Micaela Bronstein 1 , Valeria Ziegler 1 , Cristian Wood 2 , Mauricio T. Caballero 1,3 , Diego Wappner 4,5 , Romina Libster 1,4 , Gonzalo Perez Marc 2,4 , Fernando P. Polack 1,4 1 INFANT Foundation, Buenos Aires, Argentina 2 Hospital Militar Central, Buenos Aires, Argentina 3 Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina 4 iTrials, Buenos Aires, Argentina 5 Swiss Medical Group, Buenos Aires, Argentina First published: 27 Aug 2021, 5:143 https://doi.org/10.12688/gatesopenres.13357.1 Latest published: 27 Aug 2021, 5:143 https://doi.org/10.12688/gatesopenres.13357.1 v1 Abstract Background: SARS-CoV-2 infected individuals ≥60 years old have the highest hospitalization rates and represent >80% fatalities. Within this population, those in long-term facilities represent >50% of the total COVID-19 related deaths per country. Among those without symptoms, the rate of pre-symptomatic illness is unclear, and potential predictors of progression for symptom development are unknown. Our objective was to delineate the natural evolution of asymptomatic SARS-CoV-2 infection in elders and identify determinants of progression. Methods: We established a medical surveillance team monitoring 63 geriatric institutions. When an index COVID-19 case emerged, we tested all other eligible asymptomatic elders ≥75 or >60 years old with at least 1 comorbidity. SARS-CoV-2 infected elders were followed for 28 days. Disease was diagnosed when any COVID-19 manifestation occurred. SARS-CoV-2 load at enrollment, shedding on day 15, and antibody responses were also studied. Results: After 28 days of follow-up, 74/113(65%) SARS-CoV-2-infected elders remained asymptomatic. 21/39(54%) pre-symptomatic patients developed hypoxemia and ten pre-symptomatic patients died(median day 13.5,IQR 12). Open Peer Review Reviewer Status AWAITING PEER REVIEW Any reports and responses or comments on the article can be found at the end of the article. Gates Open Research Page 1 of 8 Gates Open Research 2021, 5:143 Last updated: 27 AUG 2021